What tool do you use to monitor your servers?
I have a simple ubuntu 12.04 server that runs nginx, gunicorn and some python WSGI websites. Every morning i want to see server's CPU and memory usage for past 24hrs so i can detect abnormalities / problems. Also, if i post on reddit about some sites on this server, i want to examine current cpu/memory usage graph.
What tools and apps are used for such task? I'm sure it's a very popular task and every server owner somehow solves it.